I'm running an app at www.universitytutor.com which lets people find tutors. Most of the tutors are college students.

We send out a follow up email 2 weeks after someone contacts a tutor to ask how it went and currently 70% of them say the tutor never responded to their inquiry!

So I'm trying to figure out how we can improve the deliverability of emails to our tutors. We're running postfix on ubuntu. Here is all the stuff I've checked:

The server IP (67.207.137.223) is not on any blacklists

RDNS is configured correctly and resolves to a FQDN

we have SPF records in place

using DKIM signatures on outgoing emails

The volume is still pretty low (maybe 500 messages per day). And most of them are unique where one person contacted another with a specific inquiry, so it's not bulk mail. I've spot checked the messages going through the site (for tutoring jobs) and they are legitimate, warranting a response and a possible job for the tutor. I can't see any reason why they wouldn't respond if they had actually gotten the email.

All the tutors had to click a confirmation link in an email when they created their account so I KNOW they got at least one email from us. We also automatically take down tutor profiles when someone reports they didn't respond. So I don't think it's a situation that built up over time where most of the tutors have graduated and are now gone. 70% is too high to be explained just by that.

I've wondered if it could be something special with university email servers? Most of the tutors are college students and have .edu email addresses. Is there anything special to worry about here in terms of deliverability to .edu mail servers?

Or am I missing something else with my mail server configuration that is causing these messages to get lost in spam filters?

Let me know if there is any other info I can provide which might be helpful.

P.S. When sending test messages to myself from the site they always come through (Gmail shows a 'pass' in the headers for both SPF and DKIM). I've tested it with Gmail and Yahoo which both work but obviously I can't get an account on their .edu mail servers to see if it works there.

Wow thanks for the thoughtful response! I'm using tools to analyze the postfix logs, the emails appear to be delivered (bounce, rejected, etc are very low). To reply, tutors can just hit reply in their email program (I use the reply-to address so the From address is consistent but they don't have to come back to my website to reply or anything like that. There is no specific incentive to reply. Yes there are ratings so tutors will do poorly if they don't respond. Haven't used SMS but this is a good idea. Facebook integration would be great also. It doesn't seem related to one domain.
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Brian ArmstrongSep 30 '09 at 13:04

I help run a medium-sized university's email servers and did a similar job at another .edu (a large community college). Typically universities have email systems quite comparable to a small ISP or large corporation. Often there's a significant difference between the email service given to students versus that given to employees; ranging from lower quotas for students to completely segregated systems for students. I'm guessing the majority of your tutors are classified as "students" by the university systems.

In other words, there's nothing categorically different about universities' email systems.

We happen to run exim with an appliance/hosted spam filter system in front of our actual mail servers. I know of universities that run Exchange, hosted google, sendmail, postfix, qmail, etc... Often Exchange is limited to employees, but it might also be set up for everybody.

Do you send that confirmation email within seconds of them clicking a button that told them an email was coming? They probably looked for it immediately.

Do you have any kind of consistent sender or subject tag? Can a potential tutor that hasn't checked their email in a week quickly notice your email from out of a list of hundreds?

Is any of this during summer? We go from roughly 8000 students regularly (at least every 2 weeks) checking their campus email accounts to under 1000 during the months of June and July (first week of August, too). Basically students check their campus accounts for messages from professors and information related to signing up for classes, otherwise they ignore them and use that yahoo or gmail account they had from back in high school that all their friends know.

EDIT: Also, many students set up their email to forward to another account, meaning you have to get through two sets of spam filters and the second spam filter will be looking at both you and the university. And the university probably has problems with zombied systems in their dorms and on their wireless leaving them with a poor reputation.

As one of the email admins for a largish university (I won't say which one, but one of the common imap servers has our name in it), I would have to agree with most of this, with one possible difference between .edu and other ISPs -- many of our students forward their mail off-site. So not only would you have our spam filter to deal with, but the destination site as well (gmail, hotmail, whatever).
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ktowerSep 30 '09 at 4:10

Thanks for the response! Yes the confirmation email is sent within seconds of sign up, and we even ask them to check the spam folder if they don't see it. So it's possible they are still registering even if the email goes to their spam folder. This is a great point. The sender and subject tag are consistent. We use a reply-to (not the from) so they can easily reply to the client. I think you're right that it could just be an issue of summer of students graduating, but that 70% number is still bothering me. It seems too high to be just from students graduating. Thanks for the thoughts!
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Brian ArmstrongSep 30 '09 at 13:09

Btw, @freiheit sorry for the stalking but i was able to figure out your university based on your profile. We have 16 tutors signed up there. But no complaints of non-response from those 16. So maybe everything is working correctly there.
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Brian ArmstrongSep 30 '09 at 13:30

@ktower good point about the forwarding; forgot about that. We don't allow forwarding because of those issues (and that we send "official communications" to students through email).
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freiheitSep 30 '09 at 15:04

I think I finally figured out what was wrong. My outgoing messages were HTML but the HTML was not standards compliant (it was just like a plain text but with some BR tags in it, no headers, etc) and there was no accompanying plain text part of the message.

I switched to just sending out plain text emails, and deliverability seems to be improving dramatically. Still a little too early to tell for sure but I'm starting to get a strong feeling that was it.

This is obvious in hindsight, but it was rarely talked about in any of the things I read so I didn't think to check. Apparently:
* plain text is the most reliable if you really need to get through spam filters
* if you're going to send HTML, make sure it's standards compliant and that there is an accompanying plain text part to the message as well

Can anyone else confirm/deny this about mal-formed html messages and plain text?

Good point and I suspect this is the cause too. I've emailed some of them in the past from my Gmail to try and see if they ever got the message in the first place. Most don't respond...which tells me they must have abandoned that account, or they think they are in trouble for not responding or something. It's very possible that these students are just graduating or moving for summer. I just wouldn't have expected it to be 70% not responding.
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Brian ArmstrongSep 30 '09 at 13:34

It would be odd for servers at a University to delete spam. There is that whole academic freedom thing and no one I know of would stand for anything other than simply tagging of it. Therefore, if it isn't bouncing back to you, it should be in the recipient's mail folder somewhere - unless the end user has their client filter configured to delete the spam rather than file it in junk.

You also have to battle the human factor. Many students I know of are very lazy or non-committal. Did you do something to entice them to sign up? Maybe they took the free cake and are not coming back? Getting them to respond to email if there isn't certainty of reward in it for them might be unreliable.

Another possibility you have to consider is whether your server was ever used for unsolicited email. When you recruited these tutors, was it via spam? Perhaps at that point there was a complaint. If so, the hand tweaked local spamassassin rules may have added your domain or IP to a "do not call" type of list.

I've checked my last month of logs and I don't see any traffic from your IP at our University's mail servers. Maybe you should recruit tutors from Acadia University and improve your chances!

Thanks for checking, I appreciate it. I agree, students are non-committal. To me this would account for perhaps a 20% no-response rate though, but probably not 70%. The server's IP appears to be clean and not on any blacklists. I'm running an old message through one of those content checkers in the article you linked to. I'm like 95% sure it was the malformed HTML. Deliverability rates keep going up and up now that I'm using plain text.
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Brian ArmstrongOct 29 '09 at 15:55